The present invention relates in general to a device and method for laser marking. More particularly, the present invention relates to a portable laser marking device having a small marking head which is suitable for deep and permanent marking of hard-to-reach components of assembled products, items having variable sizes, items dispersed over a wide area and/or stationary items, which marking is both very difficult to alter, and if altered, the alteration is readily detected by a casual observer.
The need to mark objects ranges from the simple requirement such as (i) for putting a name tag on an object for recognition by its owner (e.g., a school bag for a child, or a garment sent for dry cleaning), (ii) for conveying certain information to a user of the object (e.g., expiration date on a manufactured food item), and (iii) for marking an object for future identification (e.g., in case of theft) or authentication (e.g., in case of art items).
Many methods for marking objects presently exist, the most common being printing the information either directly on the object, or on a separate sticker which is thereafter attached to the object. In many cases this level of marking is satisfactory, either because the duration of time the marking is expected to survive is limited, such as in the case of short lived shelf items, or in cases where there is no significant risk involved if the marking is altered.
However, other situations exist, where permanent marking is necessary, such that it is both very difficult to alter the marking, and if such an alteration is attempted, it may be readily detected by a casual observer.
It is clear that a detachable sticker cannot serve the purpose of a permanent marking means, as it can be removed, or replaced by another sticker. Even if the removal and replacement of the sticker can eventually be traced and detected in a laboratory, the purpose of immediate detection by an observer is not fulfilled.
Theft of motor vehicles is a well known problem all over the world. The standard way to combat theft is by making it difficult to start and move a parked vehicle by a variety of active and passive protection schemes, and indeed many such schemes are presently marketed globe wise. The usefulness of these schemes, however, is limited, and even though the vast majority of vehicles are protected, the epidemic of vehicle theft is ongoing and increasing. The stolen vehicles are used for joyrides and/or resale, but mostly for the stripping of parts for resale of the stripped parts. The stolen vehicles are therefore disassembled, and the parts are resold as spare parts.
Law enforcing agencies find it difficult to stop this trade in stolen property, as it is virtually impossible to prove that a certain spare part (e.g., a vehicle door) was stolen from a specific vehicle, and therefore it is very difficult to convict the thief, the merchant or the user of the stolen goods.
Engine blocks, chassis, and possibly other components may be marked by the original producer, but these markings are located in difficult places, and may not be directly related to the declared identity of the vehicle (referred hereinafter as the vehicle identification code, typically the vehicle identification number (VIN) and/or its license plate number), and are therefore not very useful for immediate identification of stolen property in the field.
Few years back a sand-blasting based marking method was developed and employed for marking a vehicle identification code on various parts thereof. Nevertheless, this method failed as an anti-theft approach, since as far as metal surfaces are of concern, sand blasting is limited to highly superficial marking which can be easily disguised by simple procedures (e.g., repainting the surface, etc.).
Laser systems are known for quite a while and are used in many fields such as but not limited the field of medicine, weapon systems, detection systems, etc. Laser systems are also used for marking various information on objects. Presently used laser marking systems are based on a relatively large stationary chassis, where the marking head is fixed in space and the objects to be laser marked are fed (manually or automatically) into the laser system. The marking is usually done on a single plane and the entire object to be marked enters the system, thus limiting laser marking to small size objects.
Such a prior art laser system 10 is depicted in FIG. 1 and typically includes (i) a control cabinet 12, which houses the laser power supply and a computer, and is connected to an external water system; (ii) a laser head 14, which is connected to control cabinet 12 by electrical and internal water cooling lines, indicated by 16; and (iii) a marking head 18, typically formed as an integral part and in continuation to laser head 12, from which marking head 18 a laser beam 20 emits.
The operation of system 10 is as follows. Laser head 12 and marking head 18 are stationary placed above a marked field in which an object 22 to be marked is placed.
Two alternative methods are used for marking, both methods employ a two dimensional displacement system to generate a relative displacement between laser beam 20 and object 22, to enable obtainment of two dimensional laser marks.
According to the first method, object 22 is placed on a conveyor 24 which displaces object 22 along a first Cartesian displacement mode, say X, as indicated by arrows 26 and 28, whereas marking head 18 is capable of changing the direction of beam 20 such that beam 20 may follow a second Cartesian displacement mode, say Y, as indicated by arrows 30 and 32. Thus, as conveyor 24 displaces object 22 along displacement mode X, beam 20 is displaced at displacement mode Y and a two dimensional mark is formed on object 22. The first method is suitable for marking products on manufacturing lines such as last marketing date on food items and expiration date on medicines.
According to the second method, object 22 is stationary placed relative to marking head 18. In this case marking head 18 is capable of changing the direction of beam 20 along both the first (X) and the second (Y) Cartesian displacement modes to form a two dimensional mark on object 22. The second method is suitable for marking items which are not manufactured in lines.
According to both methods, the relative displacement along the first and second Cartesian displacement modes between beam 20 and object 22 is under the control of the computer housed in control cabinet 12.
Nevertheless the prior art marking systems suffer limitations rendering them not suitable for some marking purposes. First, such systems require an external water cooling system, employ large laser heads which require stationary support and are therefore robust and non-portable. Typical dimensions of such systems (in mm) are indicated in FIG. 1. Second, as a result of the robustness and non-portability of the systems, such systems are not suitable for marking hard-to-reach components of assembled products such as vehicle parts, items which have varying sizes, items dispersed over a wide area and/or stationary items.
There is thus a widely recognized need for, and it would be highly advantageous to have, a portable laser marking system having a small marking head which is suitable for deep and permanent marking of hard-to-reach components of assembled products, items having variable sizes, items dispersed over a wide area and/or stationary items, which marking is both very difficult to alter, and if altered, the alteration is readily detected by a casual observer.
According to the present invention there is provided a portable device and method for deep and permanent laser marking of hard-to-reach components of assembled products, items having variable sizes, items dispersed over a wide area and/or stationary items, which marking is both very difficult to alter, and if altered the alteration is readily detected by a casual observer.
According to further features in preferred embodiments of the invention described below, the laser marking device comprising (a) a control cabinet including a built-in laser generating unit; (b) a marking head formed as a portable unit for marking the object with the laser mark; and (c) a flexible laser delivery system optically connecting said laser generating unit and said marking head.
According to still further features in the described preferred embodiments provided is a laser marking head for permanently marking a laser mark on an object, the marking head comprising (a) a two dimensional laser scanning system; (b) a collimating optical system for collimating a laser output of a laser delivery system and directing the laser output at the two dimensional laser scanning system; (c) a focusing system for receiving the laser output from the two dimensional laser scanning system and focusing the output onto the object; and (d) a focusing support for keeping the object at a focus distance from the marking head. According to still further features in the described preferred embodiments the control cabinet is portable.
According to still further features in the described preferred embodiments the device further comprising a computer system for controlling marking of the object.
According to still further features in the described preferred embodiments the built-in laser generating unit is air-cooled.
According to still further features in the described preferred embodiments the built-in laser generating unit generates Q-switched laser pulses generated by a I flash lamp or a diode pumped laser.
According to still further features in the described preferred embodiments the flexible laser delivery system is selected from the group consisting of an articulated Irm (e.g., seven knee type arm) and an optical fiber.
According to still further features in the described preferred embodiments the optical fiber has a low numerical aperture.
According to still further features in the described preferred embodiments the optical fiber is all-silica fiber.
According to still further features in the described preferred embodiments the marking head includes a collimating optical system for collimating a laser output of the flexible laser delivery system.
According to still further features in the described preferred embodiments the marking head includes a two dimensional laser scanning system.
According to still further features in the described preferred embodiments the two dimensional laser scanning system includes a first and a second rotatable mirrors rotating about a first and a second axes, respectively.
According to still further features in the described preferred embodiments the first mirror is rotated via a first motor, whereas the second mirror is rotated via a second motor.
According to still further features in the described preferred embodiments the first and second motors are closed loop galvanometric motors.
According to still further features in the described preferred embodiments the marking head includes a focusing system.
According to still further features in the described preferred embodiments the focusing system is a focusing lens of an F-theta type, which serves at focusing the laser beam onto the marked object.
According to still further features in the described preferred embodiments the marking head includes a focusing support for keeping the surface of the marked object at a focus distance.
According to still further features in the described preferred embodiments the focusing support includes at least three prongs.
According to still further features in the described preferred embodiments the device further comprising at least three sensors (e.g., microswitches) serving as interlocks to ensure operation only when the marking head is held in place and at a correct focus distance from the marked object.
According to still further features in the described preferred embodiments the marking head includes a handle equipped with a marking on/off control device.
According to still further features in the described preferred embodiments provided is a method of laser marking an object comprising the steps of (a) predefining at least one position on the object; (b) using a laser marking device for marking a laser mark of a predefined design onto the object, the laser mark including a positive identification information related to the object (such as the vehicle identification code when the object is a vehicle, etc.), the laser mark being of such depth and clarity such that an attempt to alter (e.g., remove, change, damage and/or cover) the mark is detectable by an observer.
According to still further features in the described preferred embodiments the method further comprising the step of (c) identifying the object as laser protected.
According to still further features in the described preferred embodiments the object is a component of a vehicle and the design is the vehicle identification code (e.g., the vehicle identification number and/or the license plate number of the vehicle).
According to still further features in the described preferred embodiments provided is a method of laser marking a vehicle for anti-theft purposes comprising the steps of (a) pre-defining at least one position on the vehicle; (b) using a laser marking device for marking a laser mark including the vehicle identification code onto the vehicle, the laser mark being of such depth and clarity such that an attempt to alter (e.g., remove, change, damage and/or cover) the mark is detectable by an observer.
According to still further features in the described preferred embodiments the method further comprising the step of (c) identifying the vehicle as laser protected.
The present invention successfully addresses the shortcomings of the presently known configurations by providing a portable laser marking system having a small marking head which is suitable for deep and permanent marking of hard-to-reach components of assembled products, items having variable sizes, items dispersed over a wide area and/or stationary items, which marking is both very difficult to alter, and if altered is readily detected by a casual observer.